1. Field of the Invention
The invention relates to a drive system for a motor vehicle and to a motor vehicle having such a drive system. The invention can be applied to any motor vehicle, but will be described with respect to a passenger motor vehicle.
2. Description of the Related Art
A hybrid vehicle generally has a hybrid drive system with plural drive units, such as an internal combustion engine and an electric machine. A parallel hybrid drive system generally is used in a hybrid vehicle to generate the highest possible energy efficiency level. The parallel hybrid drive system permits the electric machine and the internal combustion engine to apply torque to a transmission either alternately or cumulatively. Furthermore, the electric machine can be used as a generator, i.e. braking energy of the vehicle, which is present in the form of kinetic energy when the vehicle is braked, can be recovered and used, for example, to charge an electric energy store. Operation of the internal combustion engine under frequent load changes results in increased fuel consumption and emission of pollutants. Hence, frequent starting and acceleration processes, which usually occur in town traffic, preferably are carried out or supported by the electric machine of a hybrid vehicle. The electric machine and the connection of the electric machine to a drive system requires additional weight and installation space as compared to a motor vehicle without a hybrid drive system. Thus, it is desirable to make a hybrid drive system as compact and space-saving as possible.
DE 44 31 929 C1 describes a drive system for a drive axle of a hybrid vehicle that has an internal combustion engine and an electric machine. The drive system is arranged transversely with respect to the direction of travel of the motor vehicle and in the region of the drive axle of the motor vehicle. A crankshaft of the internal combustion engine optionally can be connected to the drive axle of the motor vehicle via a clutch and a transmission together with an intermediate shaft. A drive shaft of the electric machine is connected continuously to the drive axle of the motor vehicle via a gear mechanism and a generator is arranged on the crankshaft of the internal combustion engine, structurally separated from the electric machine. However, this arrangement is disadvantageous because the parallel arrangement of the shaft of the electric machine, the shaft of the generator and the drive shaft requires a relatively large installation space for the drive system. Furthermore, a drag torque disadvantageously is generated when the electric machine is not in the electric motor operating mode due to the continuous connection of the electric machine to the drive axle.
The invention is therefore based on the object of providing an improved drive system that eliminates the above-mentioned disadvantages.